Introduction
Literature
Data
Methodology
Results
Hypothesis:
A biased media reporting in political news may have a profound influence on voter opinions and preferences
The concept of media bias encompasses different subtypes (D’Alessio and Allen, 2000): (1) Coverage bias, (2) Tonality bias, (3) Agenda bias
Research Question:
Is online media biased?
What is the effect on voting behavior?
Methodology:
Unbiased reporting:
Biased reporting:
To what extend does a reporting deviate from that benchmark?
What is the benchmark?
Coverage bias (Quantity: How often do political actors appear in the media?)
Tonality bias (Quality: How are parties evaluated?)
Agenda bias (Quality: Is a party able to present their own political positions in the media?)
Hypothesis:
Benchmark:
The amount of a parties campaign communication (Hopmann et al., 2012)
Standing in polls (Junqué de Fortuny et al., 2012)
Average visibility of all parties in each media outlet (Eberl et al., 2017)
Methodology:
Manually coded data
Textmining approach (e.g. count number of occurrences)
To estimate the effect of the bias on voting preferences…
Historial data (Dewenter et al., 2018)
Hypothesis:
Benchmark:
Methodology: - Manually coded data (Eberl et al., 2017)
Hypothesis:
Benchmark:
Methodology:
Results:
Online news articles
A party \(p\) is treated as visible in an article of newspaper \(s\) if the party itself is mentioned in an article (if an article contains the word “SPD”, “CDU”/“CSU/Union”,“FDP”,“Grüne”,“AfD” or “Linke”)
\[ \text{visibility}(p,s) = \frac{\text{#Articles}_{p,s}}{\text{#Articles}_s} \]
{width:80%}
There is a bias in a medium when a political party is overrepresented compared to other parties and other outlets
Benchmark: Average visibility of all parties in each media outlet during the period of analysis
Visibility bias: Deviation of each party’s specific visibility from the average visibility of all other parties in that outlet.
Dictionary-based method to measure the tone (or sentiment) of a document.
Dictionary is a list of words associated with positive and negative polarity weighted within the interval of \([-1; 1]\)
| word | value | |
|---|---|---|
| 1 | unsozial | -0.4614 |
| 2 | exotisch | 0.1944 |
| 3 | mürrisch | -0.4658 |
| 4 | mau | -0.1914 |
| 5 | schmutzig | -0.2984 |
| 6 | mut | 0.6093 |
| 7 | dilemma | -0.3403 |
| 8 | unsinn | -0.4969 |
| 9 | befürchten | -0.3602 |
| 10 | entsetzlich | -0.477 |
Agenda bias refers to the extent to which political actors appear in the public domain in conjunction with the topics they wish to emphasize.
Benchmark: Policy issues addressed in party press releases as an approximation of the potential universe of news stories. .
Credits: Christine Doig
Credits: Blei (2012)
\(K\): choose the number of topics
\(\theta_d\): for each document \(d\), choose a distribution over topics;
\(z_{d,n}|\theta_d\): according to \(\theta_d\), assign a topic \(z_{d,n}\) for the \(n^{th}\) word;
\(w_{d,n}|z_{d,n},\beta,\theta\): choose a term from that topic according to \(\beta_k\)
\(N\): repead this process for all \(n\) word-positions in the document.
\(D\): conduct this process for all \(d\) documents in the corpus
Allows to include covariates into a topic model:
Topic Prevalence: Attributes that affect the likelihood of discussing topic \(k\)
Topic Content: Attributes that affect the likelihood of including term \(w\) overall, and of including it within topic \(k\)
| Joint label | News articles | Press releases |
|---|---|---|
| Topic 47 : staatsanwaltschaft polizei erklärt peter | staatsanwaltschaft polizei ermittlungen cdu | erklärt peter netzdg steudtner |
| Topic 8 : trump gipfel usa trump | trump gipfel hamburg donald | usa trump un nationen |
| Topic 11 : afd petri sachsen anhalt | afd petri partei frauk | sachsen anhalt poggenburg andré |
| Topic 17 : euro milliarden euro milliarden | euro milliarden millionen union | euro milliarden jahr einkommen |
| Topic 46 : türkei erdogan russland sanktionen | türkei erdogan gabriel deutschland | russland sanktionen russischen russisch |
| Topic 37 : spd koalit agenda sozial | spd koalit partei große | agenda sozial kort ungleichheit |
| Topic 30 : afd höcke meuthen bundesvorstand | afd höcke partei gauland | meuthen bundesvorstand partei verfassungsschutz |
| Topic 27 : spahn cdu gabriel macron | spahn cdu jen heimat | gabriel macron französischen deutsch |
| Topic 26 : zdf illner öffentlich medien | zdf illner sendung sender | öffentlich medien rechtlichen rundfunk |
| Topic 34 : afd weidel deutschland weidel | afd weidel gauland alic | deutschland weidel alic migranten |
For each document, we have a distribution over all topics, e.g.:
Agendas were measured in terms of percentage distributions across the 50 topics.